WordPress automatically assigns a long filename to your post, called a post slug:

/what-you-can-do-immediately-for-higher-rankings

SEO Stoppord plugin strips common words like "Att", "här" or "där" out of your post slug to make it more search engine friendly. With SEO Stoppord plugin activated, the slug for our example blog post would look like this:

/immediately-higher-rankings

The slug is generated on saving a post (so you get a chance to look at it before publishing, and change it), or on publish. It won't overwrite an existing slug. You can force a new slug generation by deleting the existing one.